It is suggested that these proteins represent the end products of the cataractous process and that they are formed as a consequence of a breakdown in the protective mechanisms of the lens. It is proposed to investigate such metabolic changes, initially, by determining the reason for the drop in reduced glutathione, and then, by working backwards down the metabolic pathways until the point, at which the changes start, is reached. Individual crosslinked polypeptides will be isolated and their properties determined in order to establish their relationships to normal lens proteins. This will include the determination of the structures of the covalent crosslinks and of the yellow and fluorescent chromophores they contain. The role of the yellow protein fraction in the structural organization of the lens and in the formation of opacities will be studied by electron microscopy.